Glass which appears green?

When looking at my computer table, I notice that when i look at the glass from above it appears to be clear/transparent to all visible colors, but when I look at the edge of the table, the glass appears to be some kind of green color.

"The green tint is caused by iron, which is an impurity in the sand used to make the glass. In the glass iron ions absorb in the red (and infra-red) and blue (and ultra-violet) parts of the spectrum, making the glass look green due to the light that is left. As other posters say, you can see this more clearly from the edge because you are looking through a greater thickness of glass. ..."